Kohn, Linda M.*; Dettman, Jeremy; Sirjusingh, Caroline; and Anderson, James B. Ecological speciation with antagonistic epistasis in experimental populations of Neurospora crassa and Saccharomyces cerevisiae: evidence for a plausible avenue of fungal speciation. In: International Meeting on "Population and Evolutionary Biology of Fungal Symbionts", Ascona, Switzerland, 2007. AB-47.

We created incipient ecological speciation in experimental populations in two stages.  First, parallel adaptation of replicate populations to two different selective environments. In Neurospora crassa, we selected from standing genetic variation from the progeny of two different crosses, crassa x crassa and crassa x intermedia. The experimental design was replicated for each cross, with 6 rounds of asexual reproduction (2 race tubes) under selection with an intervening 7 rounds of sexual reproduction under permissive conditions.  In yeast, selection was from emerging variation starting with a single isogenic diploid progenitor, and with each lineage barcoded  through 500 generations of asexual reproduction under selection and 5 rounds of sexual reproduction under permissive conditions.  In the second stage, divergent selection was demonstrated by measuring fitness of all populations reciprocally in the selective environments.  The genetic basis, antagonistic epistasis, was demonstrated in comparisons of hybrid fitness among the divergently evolved lineages with fitness in hybrids between parallel-evolved lineages.

Keywords: host shifts, domestication, ecological specialization, Dobzhansky-Muller model

*Institution: Department of Ecology and Evolutionary Biology, University of Toronto

Email: kohn@utm.utoronto.ca